This invention relates to cord wrapping and tying, and particularly to a device and method adapted for securing the end windings of the stator of an electrodynamic machine and tying a knot in the cord to secure it.
Numerous types of electrodynamic machines such as induction and synchronous type alternating current electric motors, generators, etc., include a stator having a metallic core with a multitude of windings running therethrough which develop magnetic fields necessary for operation of the device. Typically, these windings become bundled together at the axial ends of the stator. It has been found that the efficiency of the machine can be enhanced if these end windings are tightly bound together. It is further desirable to bind the end windings to prevent their interfering with other components of the device, and to properly place the windings in contact with thermally sensitive elements typically used for machine overheating protection. Automated machinery for lacing the end windings of stators are currently known. For example, U.S. Pat. No. 3,685,470, which is herein incorporated by reference, is assigned to the assignee of this invention, Link Engineering Company, and describes a machine for stator lacing. The machine described by the above-identified Link patent employs a lacing needle which interacts with a cord supply finger located within the stator bore to form loops of lacing cord around the end windings of the stator as the stator is rotatably indexed. However, with this machine and many other existing devices designed to perform this task, it is necessary for the operator to manually knot the free end of the lacing cord at the completion of the lacing sequence to prevent the cord from unravelling. The necessity for this manual procedure adds to direct labor costs, increases production cycle time, and can lead to reliability problems.
In view of the above, it is an object of this invention to provide a device and method for automatically securing the lacing cord used to bind the end windings of a stator by tying a knot in the cord at the completion of the lacing cycle. It is another object of this invention to provide such cord securing operation without substantial modification to existing lacing machinery and to provide a high degree of reliability. It is another object of this invention to provide a securing knot in lacing cord using the same machine which performs the lacing operation. It is a further object of this invention to provide additional improvements in stator lacing machines according to the prior art such as that described by the above-mentioned previously issued U.S. patent.
The above objects of this invention are achieved by providing a stator coil lacing machine having an automated control system which permits the lacing operation to proceed normally until a final lacing step at which time the rotational indexing motion of the stator ceases. The lacing needle is then controlled to undergo several steps which form the cord knot, and cause the free end of the cord to be pulled tight by a cord clamp to secure the knot. At the conclusion of the lacing cycle, the lacing cord is repositioned in the machine to enable the cycles to be repeated once a new stator is loaded in the machine. The lacing cord knot is formed without requiring substantial modifications to lacing machines constructed in accordance with the teachings of the prior art.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appendend claims, taken in conjunction with the accompanying drawings.